I know, I know - I'm from the UK, and it's very hard to let go of the over-analysing! I think here it's not so much about the school as about the individual teacher - they have a lot more autonomy here. There are of course goals for the end of each two-year cycle, but it's really up to teachers how they are going to hit them. No 'it's Term Two, Week 4 so now we're all studying the lifecycle of the earthworm' here!
All the schools along the Lake Strip between Geneva and Lausanne will be set up for non-French speakers. If you want to be rock solid sure, don't go too far inland - the villages nearest the lake are naturally the most expensive so have a higher proportion of incoming expats/local hires, who usually hold quite senior jobs and command higher salaries than the local average.
What we did was choose a house, then popped in to see the school the next morning before signing the contract. (The school was slightly puzzled by this, but welcoming in a 'sweet nutter foreigners' sort of way - it's unusual here to do viewings as of course you HAVE to go to 'that' school, so they think what's the point..?). You almost certainly won't meet the individual teachers, though, and have to take a sort of 'ommmm...' Zen approach.
For me, it's worked out fine. My kids have so far had 5 teachers between them, with year changes and job sharing, and they have ALL been fantastic - friendly, professional, enthusiastic about having my kids in their classes (native English speakers are also very popular with other parents, who want their kids to 'catch' English). My son's first teacher emailed me before the move and met us in school during the Easter holidays , so he could get to know her, see the classroom and feel at ease on the first day of term. His current teacher has done things like given him a science test in French, but allowed him to write his answers in English (because it's a science test, not a language test) as she's a fluent English speaker.
My experience is that the teachers make accommodations, are fluid, are receptive to these incomers. It's really, really an everyday thing here. I too found this notion difficult to grasp before we moved out, as we were moving from rural Somerset where almost no-one is foreign and it's almost impossible to imagine how the school would cope.
Give it a try! The kids will be a matter of minutes from school, will have local friends, will feel part of their neighbourhood for celebrations rather than seeing it as a sort of dormitory. Worst case, it won't work, and they can move with a sigh of relief into international schooling (obviously don't tell them that bit ). But it's MUCH harder to do it the other way round.
Give us a shout once you know your area, and we'll see if we have any more local knowledge between us.
kodokan